Field of the Invention
The present invention relates to the preparation of composite coatings which provide a gradient coloration in the cross-web direction. More particularly, a process for preparing a composite coating having a variable thickness in the cross-web direction is provided in which premetered coatings are simultaneously applied to a carrier film, one layer of the coating being of a uniform thickness and another layer being colored and of variable thickness in the cross-web direction when measured either from the center or an edge of the web. Coloration of the layer of variable thickness provides a gradient in the optical density of the composite which makes it suitable for use as an interlayer for providing a vignette stripe in an automobile windshield.
A premetered coating apparatus consisting of dimensionally stable and chemically inert pieces forming a coating die may be modified in accordance with the invention for use in preparing the novel coatings. A flow channel for the coating fluid is formed by openings carved into the die pieces, by openings formed when the die pieces are assembled, or both. Typical practice is to configure the interior geometry of the die so that coating fluid is extruded in a sheet of uniform thickness.